You're right about ad block. Ad block grew an insane amount (300%) in the past two years:
I really doubt any browser will start installing it by default, so I think adblock will be limited to: a) Really technical people (HNers) b) Friends of HNers that are bothered enough by the real web experience while on their friend's systems that they go ahead and install adblockers.
I don't see adblockers covering more than 10% of web users, and they're likely the least valuable 10% of web users (they may earn a lot, but they don't have burning holes in their pockets either).
The growth isn't driven by technical people any more; it's normal people who've grown up using web browsers and who don't think twice about installing an extension on Chrome. You're correct through that it is spreading through word of mouth. You can get more on the pagefair blog.
My point is that adblock usage doesn't seem to be nearly as prevalent as we assume - at work (where everybody has admin rights on their work machines) maybe 10% of the non technical users have it. The point that makes people install it seems to be youtube ads.